The present invention relates to novel oxamide derivatives, a process for their manufacture, pharmaceutical preparations containing these derivatives, and the use of these derivatives as medicaments. In particular, the present invention relates to novel oxamide derivatives which are inhibitors of inosine monophosphate dehydrogenase (IMPDH).
Inosine monophosphate dehydrogenase (IMPDH) is an enzyme involved in the de novo synthesis of guanine nucleotides. The enzyme catalyses the NAD-dependent oxidation of inosine-5′-monophosphate (IMP) to xanthosine-5′-monophosphate which is the rate limiting step in the synthesis of guanine nucleotides. As a result of the key role of the enzyme in guanine nucleotide biosynthesis, the enzyme represents an important target for the development of inhibitors which would have utility as therapeutic agents in the treatment of IMPDH related processes.
The de novo synthesis of guanine nucleotides is particularly important in B- and T-lymphocytes to provide sufficient levels of nucleotides to support a proliferative response to mitogen or antigen [Wu, J. C., Persp. in Drug Discovery and Design., 2, 185-204, (1994)]. IMPDH inhibition is thus an attractive target for selectively inhibiting the immune system. Inhibitors of IMPDH are known [Pankiewicz, K. W., Exp. Opin. Ther. Patents., 9, 55-65, (1999)], and the uncompetitive inhibitor mycophenolic acid (MPA) has been demonstrated to inhibit the response of B- and T-cells to mitogen or antigen [Allison, A. C. and Eugui, E. M., Transplant. Proc., 25, 8-18, (1993)]. MPA has therefore been utilised as an immunosuppressant.
It is also recognised that IMPDH plays a role in other rapidly proliferating cells such as tumour cell lines, indicating that IMPDH inhibition is a target for anti-cancer chemotherapy [Nagai, M. et al., 51, 3886-3890, (1990)].
IMPDH inhibition has also been shown to play a role in viral replication in some cell lines which support virus replication [Pankiewicz, K. W., Exp. Opin. Ther. Patents., 9, 55-65, (1999)]. Ribavirin, for example, is a broad spectrum antiviral agent which has been approved by the U.S. Flood and Drug Administration for use as an aerosol for infants with serious respiratory infections due to respiratory syncytial virus and is also in use as an agent for the treatment of patients infected with Hepatitis C virus when used in combination with interferon [Patterson, J. L. and Fernandez-Larsson, R., Rev. Infect. Dis., 12, 1139-1146, (1990); McHutchison, J. G. et al., New. Engl. J.Med., 339, 1549-1550, (1998)]. Ribavirin is converted in cells to ribavirin 5′ monophosphate which is an inhibitor of IMPDH.
Additionally, the IMPDH inhibitors ribavirin and MPA have been shown to inhibit the replication of yellow fever virus (a RNA virus) whilst MPA has been demonstrated to inhibit Hepatitis B virus replication (a DNA virus) in vitro supporting the broad range antiviral activity of these inhibitors [Neyts, J. et al., Antiviral Res., 30, 125-132, (1996); Gong, Z. J. et al., J. Viral Hepatitis., 6, 229-236, (1999)]. Furthermore, MPA has also been shown to potentiate the antiviral effects of nucleoside analogues both in vitro and in animal models [Neyts, J. and De Clercq, E., Inter. Antiviral News., 7, 134-136, (1999)]. Together these observations indicate that IMPDH inhibitors have utility as broad spectrum antiviral agents.
IMPDH inhibitors would therefore have therapeutic potential as immunosuppressants, anti-cancer agents and anti-viral agents. Specifically, such compounds may be used in the treatment of transplant rejection, the treatment of cancer and as antiviral agents in the treatment of viral diseases such as retroviral infections and hepatitis C virus infections (either alone or in combination with other antiviral agents such as interferon or derivatives thereof, such as conjugates with polyethylene glycol).